1、 double a,b,c; double root1,root2; boolean boo; public SquareEquation(double a,double b,double c) this.a=a; this.b=b; this.c=c; if(a!=0) boo=true; else boo=false; public void getRoots() if(boo) System.out.println(是一元2次方程); double disk=b*b-4*a*c; if(disk root1=(-b+Math.sqrt(disk)/(2*a); root2=(-b-Mat
2、h.sqrt(disk)/(2*a); System.out.printf(方程的根:%f,%fn,root1,root2);方程没有实根n不是一元2次方程 public void setCoefficient(double a,double b,double c)SunRise.java/倒包即可import tom.jiafei.*;class SunRise public static void main(String args ) SquareEquation equation=new SquareEquation(4,5,1); equation.getRoots(); equati
3、on.setCoefficient(-3,4,5);2、继承 按照前面介绍的使用Eclipse输入、编译、调试程序的步骤,输入下面程序并完成未实现的代码,然后编译、调试程序。package com.Example;public class People protected double weight,height; public void speakHello() System.out.println(yayawawa public void averageHeight() height=173;average height:+height); public void averageWeigh
4、t() weight=70;average weight:+weight); class ChinaPeople extends People /直接继承输出函数即可public void speakHello() System.out.println(你好,吃了吗 /直接调用输出函数 /只需改变数据值即可 height=168.78; /单位是汉字,需要注意添加格式 System.out.println(中国人的平均身高:+height+厘米 weight=65; /直接继承输出函数,需要注意单位的添加方式 中国人的平均体重:+weight+公斤 public void chinaGongf
5、u()/直接继承输出函数坐如钟,站如松,睡如弓 class AmericanPeople extends People /直接继承输出函数How do you do height=178.78; /直接继承输出函数美国人的平均身高: /直接继承输出函数,并注意单位的添加 weight=75;美国人的平均体重: public void americanBoxing()直拳、钩拳 class BeijingPeople extends ChinaPeople /直接继承输出函数您好 /直接继承输出函数,并注意单位的添加 height=170.78;北京人的平均身高:public void aver
6、ageWeight()/直接继承输出函数,并注意单位的添加weight=78;北京人的平均体重: public void beijingOpera() 唱腔,身段,把式,生旦净丑 public static class Example/这是本程序的主函数,程序直接来此运行,当需要计算的时候再调用上面的程序 public static void main(String args) ChinaPeople chinaPeople=new ChinaPeople(); AmericanPeople americanPeople=new AmericanPeople(); BeijingPeople
7、beijingPeople=new BeijingPeople(); chinaPeople.speakHello(); americanPeople.speakHello(); beijingPeople.speakHello(); chinaPeople.averageHeight(); americanPeople.averageHeight(); beijingPeople.averageHeight(); chinaPeople.averageWeight(); americanPeople.averageWeight(); beijingPeople.averageWeight()
8、; chinaPeople.chinaGongfu(); americanPeople.americanBoxing(); beijingPeople.beijingOpera() ; beijingPeople.chinaGongfu(); 3、接口回调按照前面介绍的使用Eclipse输入、编译、调试程序的步骤,输入下面程序并完成未实现的代码,然后编译、调试程序。package com.lishuo;interface ComputerWeight public double computeWeight();class Television implements ComputerWeight
9、 /实现computeWeight()方法。 public double computeWeight()/调用return关键词 return 1.0;class Computer implements ComputerWeight/实现computeWeight()方法。/调用return关键词 return 2.0;class WashMachine implements ComputerWeight /调用return关键词 return 3.0;class Car ComputerWeight goods; double totalWeights=0; Car(ComputerWeig
10、ht goods) this.goods=goods; public double getTotalWeights() totalWeights=0; /计算totalWeights/调用for函数进行计算for(ComputerWeight good : goods) totalWeights += puteWeight(); return totalWeights;/这是本程序的主类,程序直接来此运行,当需要计算的时候,根据主类里面的指示去上面的方法里面去计算即可public class Road ComputerWeight goodsOne=new ComputerWeight50,
11、goodsTwo=new ComputerWeight22 ; for(int i=0;igoodsOne.length;i+) if(i%3=0) goodsOnei=new Television(); else if(i%3=1) goodsOnei=new Computer(); else if(i%3=2) goodsOnei=new WashMachine();goodsTwo.length; goodsTwoi=new Television(); goodsTwoi=new Computer(); goodsTwoi=new WashMachine(); Car 大货车=new Car(goodsOne); /输出结果 大货车载货物重量:+大货车.getTotalWeights(); Car 小货车=new Car(goodsTwo);小货车载货物重量:+小货车.getTotalWeights();
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